Several publications and patent documents are cited throughout the specification in order to describe the state of the art to which this invention pertains. Each of these citations is incorporated herein by reference as though set forth in full.
The potato (Solanum tuberosum), one of the world's most important food crops, produces more dry matter and protein per hectare than the major cereals (FAOSTAT 2010; http://faostat.fao.org). In addition to direct human consumption, a large portion of the potato crop is used as animal feed, where it serves as an important source of dietary amino acids. Free amino acids account for about 50% of the total nitrogen found in potato tubers (Koch et al., 2003). However, the essential amino acid methionine (Met) is limiting when compared to the daily uptake value recommended by the World Health Organization (Woolfe et al., 1987). Thus, increasing Met levels can augment the nutritional value of potato tubers. In addition, Met is the precursor of methional, a volatile compound produced under high temperature that is the major component of the attractive aroma associated with baked potatoes, potato chips, and French fries (Lindsay, 1996). Although the taste of potato chips can be improved by free Met supplementation before frying (Chang and Reddy, 1971), the cost is considered prohibitive. Therefore, due to the associated nutritional and aroma benefits, increasing the tuber Met content is of interest to the potato industry.